1. Field of the Invention
The present invention relates to a process for isolating and purifying zirconium species. More specifically, the present invention provides a process for purifying and isolating zirconium as zirconium peroxosulfate and its use, either as is or to prepare additional zirconium species.
2. Description of the Related Art
A wide variety of zirconium species both neutral and salts are known. The chemistry and synthesis of various zirconium species has been reviewed by Blumenthal, in “The Chemical Behavior of Zirconium”, D. Van Nostrand Co., 1958. In this review, certain peroxo compounds of zirconium are disclosed. These zirconium peroxides can be prepared by adding an alkali metal hydroxide in combination with hydrogen peroxide to an aqueous solution containing zirconium salts.
In U.S. Pat. No. 4,174,418 issued to Welch et al., an insoluble peroxide complex of zirconium is described. The zirconium peroxide complex can be prepared by combining zirconyl acetate and hydrogen peroxide in an aqueous solution. In solution this mixture initially forms a gelatinous product, which is collected and then dried at about 80° C. The resulting zirconium species contains both acetyl groups and peroxide groups and can be used for a variety of medicinal uses, including as an antibacterial substance. Tarafder et al in “Novel Peroxo complexes of Zirconium Containing Organic Ligands”, Inorg. Chem., v.25, pp. 2265–2268, 1986, described synthesis of several organoperoxo complexes of Zr(IV) along with their properties with respect to oxygen transfer to various substrates; these peroxo complexes were found to be very stable. Carboxylato peroxo complexes of zirconium were prepared by Dengel et al (“Studies on Transition Metal Peroxo Complexes-IX. Carboxylato Peroxo Complexes of Niobium, Tantalum, Zirconium and Hafnium”, Polyhedron, v.8, pp. 1371–1377, 1989) through reaction of zirconyl chloride with potassium salts of oxalic, citric, tartaric and glycolic acids; the complexes' structure was investigated.
Schwarz et al. in Z. Anorg. und Allgem. Chemie, v.176, pp. 219–220, 1928 describes preparing zirconium peroxosulfate with the molar composition of Zr2(O2)3(SO4)×8H2O. The zirconium peroxosulfate was isolated as a solid crust from a solution that contained both zirconium sulfate and hydrogen peroxide. However, the solid crust did not form until the solution was maintained at about 0° C. for more than six days. Consequently, this method of preparation is highly undesirable, requiring low temperatures and very long times to isolate the final product. Additionally, the compound is provided in the form of a solid crust, which entraps a variety of byproducts, excess reagents, starting materials, and reaction solution. Consequently the initially isolated product may not be pure and requires extensive purification steps to provide a zirconium species that can be used.
Thkhomirov et al in “Precipitation of Peroxide Compounds of Zirconium from Sulfate Solutions”, Zhurnal Neorganicheskoi Khimii, v. 7, pp. 1860–1868, 1962 studied precipitation of zirconium peroxo compounds from solutions of zirconyl sulfate with hydrogen peroxide. After several days of keeping the reaction mixture at room temperature the zirconium peroxosulfate with composition Zr2(O2)3(SO4)×nH2O (n=8–10) was precipitated from the solutions with pH=0.1–0.7. According to the authors, precipitation was incomplete and the disclosed process was not able to provide efficient recovery of zirconium from the starting solution.
The above preparation was repeated by Jere et al in “Studies on Peroxo Sulfato Zirconium (IV) Complex”, J. Inorg. Nucl. Chem., v. 32, pp. 537–542, 1970 and the compound with the molar composition Zr2(O2)3(SO4)×10H2O was obtained; spectroscopic, thermal and magnetic properties of the prepared zirconium peroxosulfate were characterized and its molecular structure was proved as having the sulfato group bridging two zirconium atoms and both the triangularly linked and the bridging type peroxo groups.
Therefore, methods of preparation of the zirconium peroxosulfate compound disclosed in the prior art do not enable separation of the zirconium peroxosulfate as a pure compound with sufficient recovery of zirconium species from the starting solutions. Consequently, there is no disclosure in the prior art of any uses of the zirconium peroxosulfate, neither as is nor as an intermediate for preparation of other zirconium containing compounds.
To overcome the disadvantages associated with the art related methods of preparation of zirconium peroxo compounds the present invention provides a novel way for preparing and isolating zirconium peroxosulfate that is both economical and suitable for industrial applications therefore enabling novel ways of usage of the zirconium peroxosulfate compound.
One object of the present invention is to provide a zirconium peroxosulfate compound as a pure microcrystalline powder comprising globular particles.
Another object of the invention is to provide a process for preparing a peroxo compound of zirconium that enables preparation and isolation of zirconium peroxosulfate within a selected time period with high degree of zirconium recovery.
A further object of the invention is to provide a process for separation of zirconium from metallic and nonmetallic compounds and purification of zirconium from impurities through highly selective precipitation of zirconium from starting solutions in the form of zirconium peroxosulfate.
It is yet a further object of the invention, to provide novel ways of using the zirconium peroxosulfate compound as intermediate zirconium species for preparing other zirconium containing compounds such as sulfate-free peroxo zirconium derivatives, zirconium dioxide and stabilized zirconia powders in the tetragonal or cubic crystalline phase.
Other objects and advantages of the invention will become apparent to one skilled in the art on a review of the specification, figures and claims appended hereto.